The present invention is directed to the provision of an inhalable formulation containing one or more APIs for the treatment of respiratory disorders such as asthma or COPD. A range of classes of medicaments have been developed to treat respiratory disorders and each class has differing targets and effects. A common feature of inhalable medicaments is that they must penetrate deep into the lung in order to reach their site of action.
To this end, the APIs are micronised, e.g. by jet milling, in order to obtain particles having the required size, typically a mass median aerodynamic diameter (MMAD) of 1-5 μm. However, the energy imparted to the particles of the API by the micronisation technique often leads to the introduction of amorphous character into the otherwise crystalline material of the API particles. Regions of amorphous character are generally regarded in the art as being undesirable, primarily because they have a tendency to absorb water leading to agglomeration of the API particles. This unpredictability detrimentally affects the particle size distribution (PSD) of the API which in turn affects the amount of fine particles of API reaching the lungs, quantified by the fine particle fraction (FPF), as determined using an impactor.
Various techniques have been proposed to remove these regions of amorphous character from micronised API particles. They typically involve recrystallising the amorphous region by exposing the micronised particles to a humid environment. See, for example, the discussion of this approach in Particulate Interactions in Dry Powder Formulations for Inhalation, X. M. Zeng et al., Taylor & Francis, London, 2000.
However, there remains a need in the art for alternative and improved approaches.